SCOPE: signal compensation for low-rank plus sparse matrix decomposition for fast parameter mapping.
Abstract Magnetic resonance (MR) parameter mapping is useful for many clinical applications. However, its practical utility is limited by the long scan time. To address this problem, this paper developed a novel image reconstruction method for fast MR parameter mapping. The proposed method (SCOPE) used a low-rank plus sparse model to reconstruct the parameter-weighted images from highly undersampled acquisitions. A signal compensation strategy was introduced to promote low rankness along the parametric direction and thus improve the reconstruction accuracy. Specifically, compensation was performed by multiplying t...
Source: Physics in Medicine and Biology - August 17, 2018 Category: Physics Authors: Zhu Y, Liu Y, Ying L, Peng X, Wang YJ, Yuan J, Liu X, Liang D Tags: Phys Med Biol Source Type: research

Single-shot Talbot-Lau X-ray dark-field imaging of a porcine lung applying the moir é imaging approach.
Single-shot Talbot-Lau X-ray dark-field imaging of a porcine lung applying the moiré imaging approach. Phys Med Biol. 2018 Aug 17;: Authors: Seifert M, Ludwig V, Gallersdoerfer M, Hauke C, Hellbach K, Horn F, Pelzer G, Radicke M, Rieger J, Sutter SM, Michel T, Anton G Abstract Talbot-Lau X-ray imaging provides additionally to the conventional attenuation image, two further images: the differential phase-contrast image which is especially sensitive to differences in refractive properties and the dark-field image which is showing the X-ray scattering properties of the object. Thus, in the dark-fi...
Source: Physics in Medicine and Biology - August 17, 2018 Category: Physics Authors: Seifert M, Ludwig V, Gallersdoerfer M, Hauke C, Hellbach K, Horn F, Pelzer G, Radicke M, Rieger J, Sutter SM, Michel T, Anton G Tags: Phys Med Biol Source Type: research

A new inverse planning formalism with explicit DVH constraints and kurtosis-based dosimetric criteria.
Abstract In inverse planning processes of radiotherapy, dose-volume histograms (DVH) have been commonly used as a measure of plan quality. The exact mathematical formulation of DVHs involves binary variables and is therefore intrinsically nonconvex. In view of the resulting computational intractability, existing treatment planning systems adopt convex surrogate models that involve many tweaking parameters. Manual parameter tweaking is then required to determine reasonable values for those parameters in order to generate plans that meet the target DVHs. However, conventional convex formulations for inverse planning...
Source: Physics in Medicine and Biology - August 17, 2018 Category: Physics Authors: Liu H, Chen Y, Lu B Tags: Phys Med Biol Source Type: research

Design and performance of the micro-dose calibrator.
Abstract A new class of dose calibrator called a micro-dose calibrator, designed to measure radioactivity rates in the range between 1 kBq up to 370 kBq, has been designed and an 8 NaI(Tl)/photo multiplier tube (PMT) module prototype built to evaluate its performance. The design of the micro-dose calibrator is based on the concept of a segmented well counter. By segmenting a single crystal well counter into multiple crystals or segments, with each segment operated and read out independently, one can extend the operational range of a standard single crystal well counter while maintaining its accuracy and spectrogra...
Source: Physics in Medicine and Biology - August 17, 2018 Category: Physics Authors: Adler SS, Choyke P Tags: Phys Med Biol Source Type: research

Deep learning with cinematic rendering: fine-tuning deep neural networks using photorealistic medical images.
Abstract Deep learning has emerged as a powerful artificial intelligence tool to interpret medical images for a growing variety of applications. However, the paucity of medical imaging data with high-quality annotations that is necessary for training such methods ultimately limits their performance. Medical data is challenging to acquire due to privacy issues, shortage of experts available for annotation, limited representation of rare conditions and cost. This problem has previously been addressed by using synthetically generated data. However, networks trained on synthetic data often fail to generalize to real d...
Source: Physics in Medicine and Biology - August 16, 2018 Category: Physics Authors: Mahmood F, Chen R, Sudarsky S, Yu D, Durr NJ Tags: Phys Med Biol Source Type: research

Linear energy transfer (LET) spectra and survival fraction distribution based on the CR-39 plastic charged-particle detector in a spread-out Bragg peak irradiation by a < sup > 12 < /sup > C beam.
Linear energy transfer (LET) spectra and survival fraction distribution based on the CR-39 plastic charged-particle detector in a spread-out Bragg peak irradiation by a 12C beam. Phys Med Biol. 2018 Aug 16;: Authors: Hirano Y, Kodaira S, Souda H, Matsumura A, Torikoshi M Abstract Facilities for heavy ion therapies are steadily increasing in number worldwide. One of the advantages of heavy ions is their high relative biological effect (RBE). In a model used at NIRS (National Institute of Radiological Sciences), linear energy transfer (LET) spectra are required to estimate biological dose (physical dose...
Source: Physics in Medicine and Biology - August 16, 2018 Category: Physics Authors: Hirano Y, Kodaira S, Souda H, Matsumura A, Torikoshi M Tags: Phys Med Biol Source Type: research

The role of acquisition and quantification methods in myocardial blood flow estimability for myocardial perfusion imaging CT.
Abstract In this work, we clarified the role of acquisition parameters and quantification methods in myocardial blood flow (MBF) estimability for myocardial perfusion imaging using CT (MPI-CT). We used a physiologic model with a CT simulator to generate time-attenuation curves across a range of imaging conditions, i.e. tube current-time product, imaging duration, and temporal sampling, and physiologic conditions, i.e. MBF and arterial input function width. We assessed MBF estimability by precision (interquartile range of MBF estimates) and bias (difference between median MBF estimate and reference MBF) for multipl...
Source: Physics in Medicine and Biology - August 16, 2018 Category: Physics Authors: Eck BL, Muzic RF, Levi J, Wu H, Fahmi R, Li Y, Fares A, Vembar M, Dhanantwari A, Bezerra HG, Wilson DL Tags: Phys Med Biol Source Type: research

CASToR: a generic data organization and processing code framework for multi-modal and multi-dimensional tomographic reconstruction.
In conclusion, the proposed framework offers a substantial flexibility for the integration of new reconstruction algorithms while maintaining computation efficiency. PMID: 30113313 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 16, 2018 Category: Physics Authors: Merlin T, Stute S, Benoit D, Bert J, Carlier T, Comtat C, Filipovic M, Lamare F, Visvikis D Tags: Phys Med Biol Source Type: research

Cascaded atrous convolution and spatial pyramid pooling for more accurate tumor target segmentation for rectal cancer radiotherapy.
In conclusion, the proposed CAC-SPP which could extract high-resolution features with large receptive fields and capture multi-scale context yields improve the accuracy of segmentation performance for rectal tumors. PMID: 30109986 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 15, 2018 Category: Physics Authors: Men K, Boimel P, Janopaul-Naylor J, Zhong H, Huang M, Geng H, Cheng C, Fan Y, Plastaras JP, Ben-Josef E, Xiao Y Tags: Phys Med Biol Source Type: research

Dose evaluation of fast synthetic-CT generation using a generative adversarial network for general pelvis MR-only radiotherapy.
Abstract To enable magnetic resonance (MR)-only radiotherapy and facilitate modelling of radiation attenuation in humans, synthetic-CT (sCT) images need to be generated. Considering the application of MR-guided radiotherapy and online adaptive replanning, sCT generation should occur within minutes. This work aims at assessing whether an existing deep learning network can rapidly generate sCT images to be used for accurate MR-based dose calculations in the entire pelvis. A study was conducted on data of 91 patients with prostate (59), rectal (18) and cervical (14) cancer who underwent external beam radio...
Source: Physics in Medicine and Biology - August 15, 2018 Category: Physics Authors: Maspero M, Savenije MHF, Dinkla AM, Seevinck PR, Intven MPW, Juergenliemk-Schulz IM, Kerkmeijer LGW, Van den Berg CAT Tags: Phys Med Biol Source Type: research

A key-point based real-time tracking of lung tumor in X-ray image sequence by using difference of Gaussians filtering and optical flow.
In this study, a new key point-based tumor tracking method, which is sufficiently fast and accurate, is presented. Given an X-ray image sequence, the proposed method employs a difference of Gaussians filtering technique to detect key points, which are robust against noise and outliers in the subsequent frames, in the tumor region of the first frame. In the subsequent frames, the key points are tracked by using a fast optical flow technique, and the tumor motion is estimated by the key points movements. To evaluate the performance, the proposed method was tested on several clinical kV and MV X-ray image sequences. The e...
Source: Physics in Medicine and Biology - August 15, 2018 Category: Physics Authors: Ichiji K, Yoshida Y, Homma N, Zhang X, Bukovsky I, Takai Y, Yoshizawa M Tags: Phys Med Biol Source Type: research

An unsupervised convolutional neural network-based algorithm for deformable image registration.
In conclusion, DCIGN is able to maintain high accuracy in the presence of CBCT noise contamination, while simultaneously preserving high computational efficiency. PMID: 30109996 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 15, 2018 Category: Physics Authors: Kearney VP, Haaf S, Sudhyadhom A, Valdes G, Solberg TD Tags: Phys Med Biol Source Type: research

Developing an efficient phase-matched attenuation correction method for quiescent period PET in abdominal PET/MRI.
In conclusion, we demonstrated that a data acquisition of 30 seconds achieved phase-matched &lt;i&gt;μ&lt;/i&gt;-maps when using specialized CIRCUS data sampling and phase-matched &lt;i&gt;μ&lt;/i&gt;-maps improved PET&lt;sub&gt;Q&lt;/sub&gt; quantification significantly. PMID: 30106008 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 14, 2018 Category: Physics Authors: Yang J, Liu J, Wiesinger F, Menini A, Zhu X, Hope TA, Seo Y, Larson PEZ Tags: Phys Med Biol Source Type: research

Self-adaptive ultrasonic beam amplifiers: application to transcostal shock wave therapy.
Abstract Ultrasound shock wave therapy is increasingly used for non-invasive surgery. It requires the focusing of very high pressure amplitude in precisely controlled focal spots. In transcostal therapy of the heart or the liver the high impedance mismatch between the bones and surrounding tissues gives rise to strong aberrations and attenuation of the therapeutic wavefront, with potential risks of injury at the tissue - bone interface. An adaptive propagation of the ultrasonic beam through the intercostal spaces would be required. Several solutions have been developed so far, but they require a prior knowledge of...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Robin J, Simon A, Arnal B, Tanter M, Pernot M Tags: Phys Med Biol Source Type: research

Ionization chamber dosimetry based on < sup > 60 < /sup > Co absorbed dose to water calibration for diagnostic kilovoltage x-ray beams.
Ionization chamber dosimetry based on 60Co absorbed dose to water calibration for diagnostic kilovoltage x-ray beams. Phys Med Biol. 2018 Aug 13;: Authors: Araki F, Ohno T, Umeno S Abstract The purpose of this study was to develop a new ionization chamber dosimetry formalism for diagnostic kilovoltage x-ray beams based on a 60Co absorbed dose-to-water calibration coefficient . To validate the new chamber dosimetry, 39 fluence spectra of kilovoltage x-rays were calculated, using a SpekCalc program, for Al half-value-layer (Al-HVL) values of 1.4 8.5 mm and tube voltages of 50 137.6 kVp. We used these sp...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Araki F, Ohno T, Umeno S Tags: Phys Med Biol Source Type: research

The multigaussian method: a new approach to mitigating spatial heterogeneities with multichannel radiochromic film dosimetry.
In this study, the abilities of various single channel and multichannel methods to reduce spatial heterogeneities, with and without scanning before irradiation, were tested. Red, green and blue single channel models, two additive channel independent perturbation (CHIP) models and two multiplicative CHIP models were compared with the Multigaussian method. The Multigaussian method is a new approach to multichannel dosimetry, based on experimental findings. It assumes that the probability density function of the response vector formed by the pixel values of the different color channels, including irradiated and non-irradiated...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Mendez I, Polsak A, Hudej R, Casar B Tags: Phys Med Biol Source Type: research

Coronary artery calcium quantification using contrast-enhanced dual-energy computed tomography scans in comparison with unenhanced single-energy scans.
Abstract Extracting coronary artery calcium (CAC) scores from contrast-enhanced computed tomography (CT) images using dual-energy (DE) based material decomposition has been shown feasible, mainly through patient studies. However, the quantitative performance of such DE-based CAC scores, particularly per-stenosis, is underexamined due to lack of reference standard and repeated scans. In this work we conducted a comprehensive quantitative comparative analysis of CAC scores obtained with DE and compare to conventional unenhanced single-energy (SE) CT scans through phantom studies. Synthetic vessels filled with ...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Li Q, Berman BP, Hagio T, Gavrielides MA, Zeng R, Sahiner B, Gong Q, Fang Y, Liu S, Petrick NP Tags: Phys Med Biol Source Type: research

Characterization of a binary system composed of luminescent quantum dots for liquid scintillation.
This study aims to establish the profile of CdSe colloidal quantum dots (cQDs) that were given the role of the fluorophore in a binary liquid scintillation system. We chose to investigate the cQDs because of their wide absorption spectrum, the tunability of their absorption and emission spectra with respect to their size and composition, and their ability to function as an effective energy transfer intermediate. The scintillation intensity and spectral response of three organic solvent-based liquid cQD dispersions have been investigated upon irradiation with kV and MV photon beams. The solvents used to disperse the cQDs we...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Delage MÈ, Lecavalier MÈ, Larivière D, Allen CN, Beaulieu L Tags: Phys Med Biol Source Type: research

Application of plastic scintillating fibres to surface dosimetry in megavoltage photon and electron beams: considerations for Cerenkov correction.
In this study a maximum error of 12% was observed for 16 MeV with a gantry angle of 45°. It was shown that the cause of this error was a non-negligible emission of Cerenkov radiation from the scintillator itself. This error was not observed when the PSD was oriented perpendicular to the plane of rotation. Similarly, the full spectral method was effective in isolating the scintillation-only signal regardless of PSD orientation. PMID: 30101759 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Monajemi TT, Avila Ruiz E Tags: Phys Med Biol Source Type: research

Exploration and application of phenomenological RBE models for proton therapy.
Conclusion: There were considerable variations between the estimations of RBE and RBE-weighted doses from the different RBE models. These variations were a consequence of fundamental differences in experimental databases, model assumptions and regression techniques. The results from implementation of RBE models in dose planning studies should be evaluated in light of these deviations. PMID: 30102240 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Rørvik E, Fjæra LF, Dahle TJ, Dale JE, Engeseth GM, Stokkevåg CH, Thörnqvist S, Ytre-Hauge KS Tags: Phys Med Biol Source Type: research

A multi-slot coaxial microwave antenna for liver tumor ablation.
Abstract This paper presents a multi-slot coaxial antenna with a pi impedance matching network for liver tumor ablation. In order to reduce damage to surrounding healthy tissues during ablation, a multi-slot radiating part was designed to produce a near-spherical heating zone with greatly increased possibility of conformal treatment. A pi impedance matching network part was designed to match the feeding transmission line and antenna without increasing antenna size. The reflection coefficient, ablation zone shape, specific absorption rate, and temperature were determined by using a finite element electromagnetic si...
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Ge M, Jiang H, Huang X, Zhou Y, Zhi D, Zhao G, Chen Y, Wang L, Qiu B Tags: Phys Med Biol Source Type: research

Substituting gelatine with Pluronic F-127 matrix in 3D polymer gel dosimeters can improve nuclear magnetic resonance, thermal and optical properties.
In conclusion, Pluronic F-127 is an attractive co-polymer to serve as a substitute for the gelatine matrix in some 3D polymer gel dosimeters. PMID: 30102250 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 13, 2018 Category: Physics Authors: Jaszczak M, Wach R, Maras P, Dudek M, Kozicki M Tags: Phys Med Biol Source Type: research

RapidBrachyMCTPS: a Monte Carlo-based treatment planning system for brachytherapy applications.
Abstract Despite being considered the gold standard for brachytherapy dosimetry, Monte Carlo (MC) has yet to be implemented into a software for brachytherapy treatment planning. The purpose of this work is to present RapidBrachyMCTPS, a novel treatment planning system (TPS) for brachytherapy applications equipped with a graphical user interface (GUI), optimization tools and a Geant4-based MC dose calculation engine, RapidBrachyMC. Brachytherapy sources and applicators were implemented in RapidBrachyMC and made available to the user via a source and applicator library in the GUI. To benchmark RapidBrachyMC, TG-43 p...
Source: Physics in Medicine and Biology - August 10, 2018 Category: Physics Authors: Famulari G, Renaud MA, Poole CM, Evans MDC, Seuntjens J, Enger SA Tags: Phys Med Biol Source Type: research

Improved discrimination between benign and malignant LDCT screening-detected lung nodules with dynamic over static < sup > 18 < /sup > F-FDG PET as a function of injected dose.
Improved discrimination between benign and malignant LDCT screening-detected lung nodules with dynamic over static 18F-FDG PET as a function of injected dose. Phys Med Biol. 2018 Aug 10;: Authors: Ye Q, Wu J, Lu Y, Naganawa M, Gallezot JD, Ma T, Liu Y, Tanoue L, Detterbeck F, Blasberg J, Chen MK, Casey M, Carson RE, Liu C Abstract Lung cancer mortality rate can be significantly reduced by up to 20% through routine low-dose computed tomography (LDCT) screening, which, however, has high sensitivity but low specificity, resulting in a high rate of false-positive nodules. Combining PET with CT may provide...
Source: Physics in Medicine and Biology - August 10, 2018 Category: Physics Authors: Ye Q, Wu J, Lu Y, Naganawa M, Gallezot JD, Ma T, Liu Y, Tanoue L, Detterbeck F, Blasberg J, Chen MK, Casey M, Carson RE, Liu C Tags: Phys Med Biol Source Type: research

Benchtop magnetic particle relaxometer for detection, characterization and analysis of magnetic nanoparticles.
Abstract This paper presents the design, construction, and testing of a magnetic particle relaxometer (MPR) to assess magnetic nanoparticle response to dynamic magnetic fields while subjected to a bias field. The designed MPR can characterize magnetic particles for use as tracers in magnetic particle imaging (MPI), with the variation of an applied bias field emulating the scan of the MPI field free point. The system applies a high-frequency time-varying excitation field (up to 45 mT at 30 kHz), while slowly ramping a bias field (± 100 mT in 1 s). The time-resolved response of the sample is measured using an...
Source: Physics in Medicine and Biology - August 10, 2018 Category: Physics Authors: Garraud N, Dhavalikar R, Unni M, Savliwala S, Rinaldi C, Arnold DP Tags: Phys Med Biol Source Type: research

A general-threshold filtering method for improving intravoxel incoherent motion parameter estimates.
In this study, we present an image denoising method for diffusion-weighted magnetic resonance imaging (DW-MRI) data. Our aim is to improve the estimation of intravoxel incoherent motion (IVIM) parameters using denoised DW-MRI data. A general-threshold filtering (GTF) reconstruction via total variation minimization has been proposed to improve image quality in few-view computed tomography. Here, we applied the combination of GTF and total difference to image denoising. Voxel-wise IVIM analysis was performed using both real and simulated DW-MRI data. Using an institutional review board-approved protocol with written informed...
Source: Physics in Medicine and Biology - August 9, 2018 Category: Physics Authors: Lin C, Liu CC, Huang HM Tags: Phys Med Biol Source Type: research

Performance evaluation of the PET component of a hybrid PET/CT-ultrafast ultrasound imaging instrument.
ian B Abstract We recently introduced a hybrid imaging instrument, PETRUS, based on a combination of Positron Emission Tomography (PET) for molecular imaging, X-ray Computed Tomography (CT) for anatomical imaging, co-registration and attenuation correction, and Ultrafast Ultrasound Imaging (UUI) for motion-correction, hemodynamic and biomechanical imaging. In order to ensure a fine co-registration of simultaneous PET-UUI acquisitions, ultrasound probes attached to an ultrafast ultrasound scanner are operated in the field of view (FOV) of a small animal PET/CT scanner using a remote-controlled micro-positioner. Her...
Source: Physics in Medicine and Biology - August 9, 2018 Category: Physics Authors: Pérez-Liva M, Viel T, Yoganathan T, Garofalakis A, Sourdon J, Facchin C, Tanter M, Provost J, Tavitian B Tags: Phys Med Biol Source Type: research

Transducer impulse response correction for a deconvolution derived ultrasound transit time spectrum.
Abstract Propagation of ultrasound through a complex composite sample may exhibit phase interference between two or more sonic-rays if differences in transit time are less than the pulse length. The transit time spectrum of a test sample, equivalent to its impulse response, was derived through active-set deconvolution of ultrasound signals with, and without, the test sample. The aim of this study was to test the hypothesis that in cases where only the transmit ultrasound transducer's digitally-coded excitation signal is available, hence not the input ultrasound signal without the test sample, incorporation of the ...
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Al-Qahtani SM, Wille ML, Langton CM Tags: Phys Med Biol Source Type: research

Dose build-up effects induced by delta electrons and target fragments in proton Bragg curves - measurements and simulations.
Abstract Dose build-up effects in the entrance channel of proton Bragg curves were investigated in detail by means of simulations and experiments. There are two relevant dose build-up effects. Firstly, the δ-electron build-up effect which takes place in the first few millimeters of the tissue until an equilibrium state of the forwards scattered δ-electrons is reached. Secondly, the target fragment build-up effect that covers the first centimeters in the entrance channel of the proton Bragg curve. These target fragments are created in inelastic interactions of the beam protons with the target nuclei and...
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Pfuhl T, Horst F, Schuy C, Weber U Tags: Phys Med Biol Source Type: research

Improved myocardial perfusion PET imaging with MRI assisted reconstruction incorporating multi-resolution joint entropy.
Abstract Myocardial perfusion (MP) PET imaging plays an important role in risk assessment and stratification of patients with coronary artery disease. In this work, we developed an anatomy-assisted maximum a posteriori (MAP) reconstruction method incorporating a wavelet-based joint entropy (WJE) prior for MP PET imaging. Using the XCAT phantom, we first simulated three MP PET datasets, one with normal perfusion and the other two with non-transmural and transmural regionally reduced perfusion of the left ventricular myocardium. Moreover, we simulated MP PET datasets of the three cases with respiratory and cardiac (...
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Wang X, Yang B, Adams MP, Gao X, Karakatsanis NA, Tang J Tags: Phys Med Biol Source Type: research

Geometrical structures for radiation biology research as implemented in the TOPAS-nBio toolkit.
Abstract Computational simulations, such as Monte Carlo track structure simulations, offer a powerful tool for quantitatively investigating radiation interactions within cells. The modelling of the spatial distribution of energy deposition events as well as diffusion of chemical free radical species, within realistic biological geometries, can help provide a comprehensive understanding of the effects of radiation on cells. Track structure simulations, however, generally require advanced computing skills to implement. The TOPAS-nBio toolkit, an extension to TOPAS (TOol for PArticle Simulation), aims to provide user...
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: McNamara AL, Ramos-Mendez J, Perl J, Held K, Dominguez N, Moreno EB, Henthorn NT, Kirkby KJ, Meylan S, Villagrasa C, Incerti S, Faddegon B, Paganetti H, Schuemann J Tags: Phys Med Biol Source Type: research

Low-rank and sparse decomposition with spatially adaptive filtering for sequential segmentation of 2D+t vessels.
Abstract This letter proposes to extract contrast-filled vessels from the overlapped noisy complex backgrounds in X-ray coronary angiogram image sequence using low-rank and sparse decomposition. A refined vessel segmentation is finally achieved by implementing Radon-like feature filtering plus local-to-global adaptive thresholding to tackle the spatially varying noisy residuals in the extracted vessels. Based on real and synthetic XCA data, experiment results show the superiority of the proposed method over the state-of-the-art methods. PMID: 30088812 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Jin M, Hao D, Ding S, Qin B Tags: Phys Med Biol Source Type: research

Density estimation of grey-level co-occurrence matrices for image texture analysis.
In conclusion, the Gaussian mixture model is the preferred method for the first type of features (in particular for small ROIs). For the second type of features, simply using a large GLCM size is preferred. PMID: 30088815 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Garpebring A, Brynolfsson P, Kuess P, Georg D, Helbich TH, Nyholm T, Löfstedt T Tags: Phys Med Biol Source Type: research

Developing a & quot;multiPatchPET & quot; system in GATE for the PET system design with irregular geometries.
Developing a &quot;multiPatchPET&quot; system in GATE for the PET system design with irregular geometries. Phys Med Biol. 2018 Aug 08;: Authors: Chen G, Weng F, Hong X, Tao W, Zhao Z, Peng Q, Huang Q Abstract This work modified the commonly used Monte Carlo tool package GATE by developing a new "multiPatchPET" system so that GATE users will be able to easily simulate PET systems with irregular geometries. The motivation was to design a brain PET scanner with high sensitivity. It is known that the compact PET scanner with a large solid coverage angle achieves high sensitivity, and thu...
Source: Physics in Medicine and Biology - August 8, 2018 Category: Physics Authors: Chen G, Weng F, Hong X, Tao W, Zhao Z, Peng Q, Huang Q Tags: Phys Med Biol Source Type: research

Monte Carlo optimization of a microbeam collimator design for use on the small animal radiation research platform (SARRP).
Abstract Microbeam radiation therapy (MRT) is a pre-clinical, spatially-fractionated treatment modality noted for its ability to achieve a large differential response between normal and tumoral tissues. In the present study, TOPAS Monte Carlo (MC) simulations were used to optimize the design of a compact, affordable multi-slit collimator (MSC) suitable for use with the small animal radiation research platform (SARRP). MRT dose distributions in a (1×1×3)cm&lt;sup&gt;3&lt;/sup&gt; water phantom were simulated for a tungsten MSC using different focal spot sizes (0.4,3mm), beam energies (40...
Source: Physics in Medicine and Biology - August 3, 2018 Category: Physics Authors: Esplen NM, Chergui L, Johnstone CD, Bazalova-Carter M Tags: Phys Med Biol Source Type: research

A simulation approach for determining the spectrum of DNA damage induced by protons.
Abstract In order to study the molecular damage induced in the form of single-strand and double-strand breaks by the ionizing radiation at the DNA level, Geant4-DNA Monte Carlo simulation code for complete transportation of primary protons and other secondary particles in liquid water have been employed in this work. To this aim, a B-DNA model and a thorough classification of DNA damage concerning their complexity were used. Strand breaks were assumed to have been primarily originated by direct physical interactions via energy depositions, assuming a threshold energy of 17.5 eV, or indirect chemical reactions of h...
Source: Physics in Medicine and Biology - August 3, 2018 Category: Physics Authors: Mokari M, Alamatsaz MH, Moeini H, Taleei R Tags: Phys Med Biol Source Type: research

A Randomized Comparison of Radiation Therapy Techniques in the Management of Node-Positive Breast Cancer: Primary Outcomes Analysis.
Abstract PURPOSE: Although inverse-planned intensity modulated radiotherapy (IMRT) and deep inspiration breath hold (DIBH) may allow for more conformal dose distributions, it is unknown whether using these technologies reduces cardiac or pulmonary toxicity of breast radiotherapy. METHODS AND MATERIALS: A randomized controlled trial compared IMRT-DIBH versus standard, free-breathing, forward-planned, three-dimensional conformal radiotherapy in patients with left-sided, node-positive breast cancer in whom the internal mammary nodal region was targeted. Endpoints included dosimetric parameters and changes in pul...
Source: Physics in Medicine and Biology - July 19, 2018 Category: Physics Authors: Jagsi R, Griffith KA, Moran JM, Ficaro E, Marsh R, Dess RT, Chung E, Liss AL, Hayman JA, Mayo CS, Flaherty K, Corbett J, Pierce L Tags: Int J Radiat Oncol Biol Phys Source Type: research

4D dose calculation for PBS proton therapy of pancreatic cancer using repeated 4DMRI datasets.
In this study, we aim to show the feasibility of 4D treatment planning for pencil beam scanning (PBS) proton therapy of pancreatic cancer, based on repeated 4DMRI datasets and 4D dose calculations (4DDC). To investigate the dosimetric impacts of organ motion, deformation vector fields were extracted from 4DMRI, which were then used to warp a static CT of a patient, so as to generate synthetic 4DCT (4DCT-MRI). The results from 4DDC show pronounced interplay effects in the CTV with dose homogeneity d5/d95 and dose coverage v95 being 1.14 and 91%, respectively, after a single fraction of the treatment. An averaging effec...
Source: Physics in Medicine and Biology - July 18, 2018 Category: Physics Authors: Dolde K, Naumann P, Dávid C, Gnirs R, Kachelrieß M, Lomax AJ, Saito N, Weber DC, Pfaffenberger A, Zhang Y Tags: Phys Med Biol Source Type: research

Relative Patlak plot for dynamic PET parametric imaging without the need for early-time input function.
Abstract The Patlak graphical method is widely used in parametric imaging for modeling irreversible radiotracer kinetics in dynamic PET. The net influx rate of radiotracer can be determined from the slope of the Patlak plot. The implementation of the standard Patlak method requires the knowledge of full-time input function from the injection time until the scan end time, which presents a challenge for use in the clinic. This paper proposes a new relative Patlak plot method that does not require early-time input function and therefore can be more efficient for parametric imaging. Theoretical analysis proves that th...
Source: Physics in Medicine and Biology - July 18, 2018 Category: Physics Authors: Zuo Y, Qi J, Wang G Tags: Phys Med Biol Source Type: research

Prediction of chemotherapy response in ovarian cancer patients using a new clustered quantitative image marker.
In conclusion, this study demonstrates the potential of our proposed new quantitative image marker fused with the features computed from both spatial and frequency domain for a reliable prediction of tumor response to postsurgical chemotherapy. PMID: 30010611 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 16, 2018 Category: Physics Authors: Zargari A, Du Y, Heidari M, Thai T, Gunderson C, Moore K, Mannel R, Liu H, Zheng B, Qiu Y Tags: Phys Med Biol Source Type: research

Validating a Monte Carlo approach to absolute dose quality assurance for proton pencil beam scanning.
In conclusion, an automated, easy-to-use Monte Carlo calculation system has been set up. This system reproduced patient specific QA results over a wide range of cases, showing that the time consuming measurements could be reduced or even replaced using Monte Carlo simulations without jeopardizing treatment quality. PMID: 30010613 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 16, 2018 Category: Physics Authors: Winterhalter C, Fura E, Tian Y, Aitkenhead AH, Bolsi A, Dieterle M, Fredh A, Meier G, Oxley D, Siewert D, Weber DC, Lomax AJ, Safai S Tags: Phys Med Biol Source Type: research

Iterative Spectral CT Reconstruction Based on Low Rank and Average-Image-Incorporated BM3D.
Abstract In a photon counting detector integrated spectral CT scanner, the received photons are counted in several energy channels to generate the corresponding projections. Since the projection in each energy channel is generated using part of the received photons, the reconstructed channel image suffers from severe noises. Therefore, image reconstruction in spectral CT is considered as a big challenge. Because the inter-channel images are all from the same object but in different energy bins, there exists a strong correlation among these images. Moreover, it is suggested that there are similarities among various...
Source: Physics in Medicine and Biology - July 13, 2018 Category: Physics Authors: Salehjahromi M, Zhang Y, Yu H Tags: Phys Med Biol Source Type: research

A small number of objective function weight vectors is sufficient for automated treatment planning in prostate cancer.
Abstract Current practice for treatment planning optimization can be both inefficient and time consuming. In this paper, we propose a automated planning methodology that aims to combine both explorative and prescriptive approaches for improving the efficiency and the quality of the treatment planning process. Given a treatment plan, our explorative approach explores trade-offs between different objectives and finds an acceptable region for objective function weights via inverse optimization. Intuitively, the shape and size of these regions describe how "sensitive" a patient is to perturbations in objecti...
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Goli A, Boutilier JJ, Craig T, Sharpe MB, Chan TCY Tags: Phys Med Biol Source Type: research

Optimized I-values for the use with the Bragg additivity rule and their impact on proton stopping power and range uncertainty.
Conclusion: We propose a set of elemental I-values well suited for human tissues in combination with the BAR. Our model establishes uncertainties on elemental I-values and the BAR, enabling to quantify uncertainties on tissue I-values, RSP as well as particle range. This work is particularly relevant for Monte Carlo simulations where the interaction probabilities are reconstructed from elemental compositions. PMID: 29999493 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Bär E, Andreo P, Lalonde A, Royle GJ, Bouchard H Tags: Phys Med Biol Source Type: research

Suggested reference values for regional blood volumes in children and adolescents.
Abstract Estimates of regional blood volumes (BVs) in humans are needed in dosimetric models of radionuclides and radiopharmaceuticals that decay in the circulation to a significant extent. These values are also needed to refine models of tissue elemental composition in computational human phantoms of both patients and exposed members of the general public. The International Commission on Radiological Protection (ICRP) in its Publication 89 provides reference values for total blood content in the full series of their reference individuals, to include the male and female newborn, 1-year-old, 5-year-old, 10-year-old...
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Wayson MB, Leggett RW, Jokisch DW, Lee C, Schwarz B, Godwin W, Bolch WE Tags: Phys Med Biol Source Type: research

LEFMIS: Locally-oriented Evaluation Framework for Medical Image Segmentation algorithms.
Conclusion: The article shows the greater usefulness and flexibility of the proposed framework in comparison to the state-of-the-art methods. The exemplary usage of the LEFMIS with or without inter-/intra-observer variability is also presented. PMID: 29999495 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Skalski A, Jakubowski J, Drewniak T Tags: Phys Med Biol Source Type: research

Flexible optically stimulated luminescence band for 1-D < i > in vivo < /i > radiation dosimetry.
Flexible optically stimulated luminescence band for 1-D in vivo radiation dosimetry. Phys Med Biol. 2018 Jul 12;: Authors: Kim TJ, Jung K, Fahimian BP, Pratx G Abstract In vivo dosimetry helps ensure the accuracy of radiation treatments. However, standard techniques are only capable of point sampling, making it difficult to accurately measure dose variation along curved surfaces in a continuous manner. The purpose of this work is to introduce a flexible dosimeter band and validate its performance using pre-clinical and clinical X-ray sources. Dosimeter bands were fabricated by uniformly mixing BaFBr:E...
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Kim TJ, Jung K, Fahimian BP, Pratx G Tags: Phys Med Biol Source Type: research

Suitability of low density materials for 3D printing of physical breast phantoms.
Abstract Breast physical phantoms are a basic tool for the assessment and verification of performance standards in daily clinical practice of x-ray breast imaging modalities. They are also invaluable in testing and evaluation of new x-ray breast modalities to be potentially established, e.g. breast computed tomography, dual-energy breast CT and phase-contrast mammography and tomography. Nowadays, there is a lack or there are only a limited number of breast physical phantoms available for this purpose. The aim of this study is to explore a range of 3D printing materials such as resins, PLA, ABS, Nylon etc., to...
Source: Physics in Medicine and Biology - July 12, 2018 Category: Physics Authors: Ivanov D, Bliznakova K, Buliev I, Popov P, Mettivier G, Russo P, Di Lillo F, Sarno A, Vignero J, Bosmans H, Bravin A, Bliznakov Z Tags: Phys Med Biol Source Type: research

Estimation of the NEMA characteristics of the J-PET tomograph using the GATE package.
a M, Pawlik-Niedźwiecka M, Raj J, Rakoczy K, Rudy Z, Sharma S, Shivani S, Silarski M, Skurzok M, Zgardzińska BK, Zielinski M, Moskal P Abstract The novel whole-body PET system based on plastic scintillators is developed by the J-PET Collaboration. It consists of plastic scintillator strips arranged axially in the form of a cylinder, opening perspective for the cost-effective construction of the total-body PET. In order to determine properties of the scanner prototype and optimize its geometry, advanced computer simulations using the GATE software were performed. The spatial resolution, the sensitivity...
Source: Physics in Medicine and Biology - July 11, 2018 Category: Physics Authors: Kowalski P, Wiślicki W, Shopa R, Raczyński L, Klimaszewski K, Curceanu C, Czerwiński E, Dulski K, Gajos A, Gorgol M, Sharma NG, Hiesmayr BC, Jasińska B, Kapłon Ł, Kamińska D, Korcyl G, Kozik T, Krzemień W, Kubicz E, Mohammed M, Niedzwiecki S, Pał Tags: Phys Med Biol Source Type: research

Transesophageal 2D ultrasound to 3D computed tomography registration for the guidance of a cardiac arrhythmia therapy.
er JL Abstract The work aims at developing a new image-processing method to improve the guidance of transesophageal HIFU atrial fibrillation therapy. Our proposal is a novel registration approach that aligns intraoperative 2D ultrasound with preoperative 3D-CT information. This approach takes advantage of the anatomical constraints imposed at the transesophageal HIFU probe to simplify the registration process. Our proposed method has been evaluated on a physical phantom and on real clinical data. . PMID: 29992909 [PubMed - as supplied by publisher] (Source: Physics in Medicine and Biology)
Source: Physics in Medicine and Biology - July 11, 2018 Category: Physics Authors: Sandoval Z, Castro M, Alirezaie J, Bessière F, Lafon C, Dillenseger JL Tags: Phys Med Biol Source Type: research